The invention relates to a compressor or turbine type rotary machine for compressing or expanding a dangerous gas, e.g. a gas that is toxic or explosive.
Such machines are used, in particular, in chemical industries for treating natural gas, etc. . . . .
As is well known in the art, a compressor or a turbine comprises a stator in which an annular gas flow chamber is formed, a rotor mounted to rotate in said chamber, a rotary shaft on which the rotor is fixed and which extends outside the stator through a shaft passage thereof, and bearings for guiding and supporting the shaft, which bearings are mounted in the shaft passage of the stator.
Outside the stator, the rotor shaft is connected to another shaft which is a driving shaft for a compressor or which is a driven shaft for a turbine.
When such a machine is used for treating a dangerous gas, it is essential to provide gas-tight sealing and to maintain it over time, specifically for preventing gases leaking to the outside as may happen along the shaft of the rotor.
A specific object of the invention is to solve this problem in a manner that is simple, effective, and cheap.